C#截取特定长度的字符串  截取特定长度字符串，不够用...代替

   //截取特定长度字符串，不够用...代替
        public static string getStr2(string s, int l, string endStr)
        {
            string temp = s.Substring(0, (s.Length < l + 1) ? s.Length : l + 1);
            byte[] encodedBytes = System.Text.ASCIIEncoding.ASCII.GetBytes(temp);

            string outputStr = "";
            int count = 0;

            for (int i = 0; i < temp.Length; i++)
            {
                if ((int)encodedBytes[i] == 63)
                    count += 2;
                else
                    count += 1;

                if (count <= l - endStr.Length)
                    outputStr += temp.Substring(i, 1);
                else if (count > l)
                    break;
            }

            if (count <= l)
            {
                outputStr = temp;
                endStr = "";
            }

            outputStr += endStr;

            return outputStr;
        }